MMR

Matchmaking rating — the hidden number a game uses to pick opponents, distinct from the visible rank.

Every competitive game keeps a hidden rating for matchmaking. The visible rank follows it with a delay, which is why a fresh unranked account can be placed far above or below what its games suggest and why a boosted rank drifts back down. On listings MMR matters for unranked accounts ("neutral MMR") and for boosted ones ("MMR fixed").